iOS 11 GM (Golden Mater) is available for the end users these days. It’s the final test version for the upcoming iOS 11 software. But some users complained that they encountered many annoying bugs on this version, including the blank lock screen, iPod rotation issue, apps not opening etc. Uninstall iOS 11 GM on iPhone and go back to iOS 10.3.3 seems to be a good choice but not an easy task.
If you have backed up iPhone in iTunes or iCloud, you can directly restore iPhone from backup files, but all the current data could be wiped. That’s why you should try an easy iOS downgrading tool called Tenorshare ReiBoot, easily delete the iOS 11 GM from iPhone and download iOS 10.3.3 firmware package to install, all the data will be kept untouched.
I believe you have learnt how to downgrade iPhone to iOS 10.3.3 from iOS 11 GM clearly with the video above. For further questions about iOS 11, check iOS 11 Problems and Fixes to get more info.